Dendrochilum was first described in 1825 by C.L. Blume. Blume described 6 species that he found on Java and divided them into two sections. Following Blume's original descriptions a few species were described during the 19th century mainly by Lindley and Reichenbach. These species are Dendrochilum filiforme in 1840, Dendrochilum glumaceum in 1841, Dendrochilum latifolium in 1843, Dendrochilum convallariaeforme in 1843, Dendrochilum tenellum in 1843 (as Acoridium tenellum), Dendrochilum uncatum and Dendrochilum pumilum in 1855, Dendrochilum longifolium in 1856, Dendrochilumbrachyotum in 1857, Dendrochilum zollingeri in 1859, Dendrochilum magnum in 1863, Dendrochilum rhombophorum in 1877 (as Coelogyne rhombophora), Dendrochilum cobbianum in 1880 and Dendrochilum arachnites in 1882, Dendrochilum linearifolium in 1889. A number of collectors travelled through Borneo during the late nineteenth century and early twentieth century, Odoardo Beccari, George Haviland, Henry Ridley, Mary and Joseph Clemens, these collectors discovered many more species which were then described by botanists. Once the US government took over the administration of the Philippines in 1898 a more comprehensive look at the Philippine flora began. E.D. Merrill and Oakes Ames added many more species to the overall list during the early part of the 20th century. Likewise in Sumatra J.J. Smith added many new species. L.O. Williams described many new species from the 1930s into the middle of the 20th century.

The first attempt at a monograph was made by J.J. Smith, in 1904, where 43 species were recognised. This was closely followed by Pfitzer and Kranzlin, in 1907, where 72 species were recognised. Oakes Ames took an interest in Dendrochilum and critically looked at the genus. During the first 25 years of the 20th century J.J. Smith transferred Platyclinis and Acoridium back into Dendrochilum. Oakes Ames then reinstated Acoridium as its own genus in 1906. Pfitzer and Kranzlin then reinstated Acoridium as a section of Dendrochilum in 1907 before Ames reinstated Acoridium again as its own genus in 1922. L.O.Williams finally transferred Acoridium back into Dendrochilum. These changes are reflected in the synonym list for many Philippine Dendrochilum species. For a very interesting read I would recommend the first part of Ames' Illustrations and Studies in the Family Orchidaceae Facsicle 2. It appears that Ames sent some engravings of species he was about to describe to Dr. Engler for information only and to help Pftizer's monograph on the Coelogyninae. Pfitzer passed away in the mean time and Kranzlin went on to describe Ames's species sometimes using the wrong engraving. Later during the 20th century L.O. Williams took an interest in Dendrochilum and looked into section Acoridium and solved some taxonomic problems (Pedersen 1997). The last enumeration by Henrik Pedersen, Jim Comber and Jeffrey Wood was in 1997 where 270 species were recognised. Henrik Pedersen wrote a taxonomic revision of Philippine Dendrochilum in 1997 and Jeffrey Wood wrote a taxonomic revision of Borneo Dendrochilum in 2001.

There are currently 278 accepted species of Dendrochilum and 294 if recognised varieties are considered.

The Dendrochilum genus is currently divided into four subgenera and the subgenera are further divided into sections (Pedersen, Comber and Wood 1997), they are:

Subgenera 1) Dendrochilum

Subgenera 2) Acoridium

sections

Falsiloba

Acoridium

Convoluta

Heterantha

Subgenera 3) Pseudacoridium

sections

Pseudacoridium

Luzonorchis

Subgenera 4) Platyclinis

sections

Platyclinis

Eurybrachium

Cruciformia

Longicolumna

Mammosa

Mindanaorchis

Replicata

More will be added to this page in relation to Todd Barkman's dissertation (1998) in the future. Barkman's conclusions differ from the sectional placement of species by Henrik Pedersen (1997).

There are many new species still being described (Pedersen 2004) (Pedersen 2001) (Pedersen 2005) (Cootes 2009) (Cootes 2010). I know of several species in collections that are awaiting description and I have two of these species myself. There are photos of in-situ species on the internet, mainly from the Philippines, of species not yet described or formally known to science. The final page on this website is a photo page devoted to those species that have not been identified or are 'new species'.

Distribution

Dendrochilum are distributed in South East Asia, and mainly in a region known as Malesia. Dendrochilum can be found from Southern Myanmar and Thailand south through the Indonesian archipelago to New Guinea and north to the Philippines and Southern Taiwan. At the time of writing, the genus has its centre of distribution in the Philippines, Borneo and Sumatra. Currently there are 81 species (including varieties) in Sumatra, 90 (including varieties) in Borneo and 108 (including varieties) in the Philippines which are 27.65%, 30.72%and 36.86%of the genus respectively. Jeffrey Wood wrote during 2001 that 91.9% of Borneo species are endemic to that island, of which 37.9% or 33 species are endemic to Mount Kinabalu alone (Wood 2001).

Most Dendrochilum are found in lower or upper montane forest. These two altitudinal zones contain mossy cloud forest which is a favoured habitat of many Dendrochilum species. Jeffrey Wood wrote "Many species seem to favour ridge-top shrubbery and mossy elfin forest which experience variable and often harsh conditions ranging from bright sunlight to dense cloud cover or drying winds. These localities experience a large fluctuation in temperature" (Wood 2001). Henrik Pedersen provided an exceptional breakdown of Philippine species within altitudinal zones, of which I will briefly outline.

The largest Philippine species lists are from mountains within the Southern Sierra Madre and Baguio area on Luzon. These mountains have been studied and collected extensively which could explain the larger numbers of Dendrochilum. Further study is needed within Mindanao and on Palawan. New species are still being brought into cultivation or photographed in the wild on Mindanao and this island could have a much higher species list in the future. Unfortunately the political situation within Mindanao and safety on Palawan keep many botanists away. Suitable habitat exists on Palawan and further species could be found there.

On Sumatra most species have been collected within the mountainous west and northern regions of the island. The diversity centres on Sumatra are Mount Leuser National Park in Aceh Province, the Mount Talang and Mount Kerinci areas. Further study is needed of the Sumatran species, unfortunately areas of Sumatra, such as Aceh Province are politically unstable and keep botanists away.

On Java most species have been found within the mountainous western part of the island. The rainfall is consistent throughout the year in the west. Eastern Java has a wet/dry season which is not suitable for most Dendrochilum species.

On Borneo most species have been collected within the Crocker Range including Mount Kinabalu and Mount Trus Madi, Mount Pagon, Sabah's Sipitang District, the Kelabit Highlands including Mount Murud, Batu Lawi, Mount Mulu, Apo Kayan, Mount Penrissen and its surrounding mountains. Jeffrey Wood wrote "Montane area of southern and east-central Sarawak and large portions of upland Kalimantan, which are probably rich in Dendrochilum, still remain where little or no collecting has taken place" (Wood 2001). Wood also wrote that the distribution patterns of Dendrochilum within Borneo correlate with the height of the cloud, local temperature (particularly minimum temperatures), exposure and forest type (Wood 2001).

Presently there is only one species found in New Guinea, Dendrochilum longifolium. This has puzzled taxonomists because preferred habitat on that island is plenty. Jeffrey Wood wrote that the mycorrhizal relationships of many Dendrochilum species may be host specific and certain fungal partners could be absent in New Guinea (Wood 2001). Henrik Pedersen wrote an interesting piece on evolutionary interpretation (Pedersen 1997 p35). Pedersen suggested that the majority of Dendrochilum evolved after the Pleistocene which has resulted in higher endemism. The Malesian region is thought to have been cooler during the Pleistocene (van Steenis 1984) which would have seen Dendrochilum growing at lower elevation and therefore more widely dispersed at the present time. Cool growing alpine plants, such as most Dendrochilum, are currently restricted to high elevations on mountains. As mountains are seen as 'islands' within a sea of jungle for these alpine plants, dispersal would be much harder in a warmer climate. If most Dendrochilum have evolved after the Pleistocene most species would not have had the time to increase their geographical range.

The subgenus Dendrochilum has its centre of diversity on Sumatra; of the 13 species found there 11 are endemic. Three species are found on Borneo and one species within the Philippines.

The subgenus Pseudacoridium is endemic to the Philippines and the five species within the subgenus are found only on Luzon and Mindoro.

The subgenus Acoridium has its centre of diversity within the Philippines with nearly all species occurring there. Two species are found on Borneo and the subgenus is completely absent on Sumatra and Java.

The subgenus Platyclinis has its centre of diversity on Borneo. This is the most widely distributed subgenera and can be found from Burma, south to Bali, east to New Guinea and north to Taiwan.

The Philippines is the only country where all four subgenera are found.

Morphology

When describing species on this website I have preferred to use the description format of Jeffrey Wood and Henrik Pedersen. Pedersen has used the terms describing the inflorescence of de Vogel (1988) and the structure of the column of F.N. Rasmussen (1986).

Dendrochilum are sympodial orchids that can have the following floral parts

Peduncle

Rachis

Bract

Dorsal sepal

Lateral sepals

Petals

Labellum

Column

Column foot

Apical wing

Stelidia

Keels/calli

Sympodial habit

There are two main types of sympodial habit found in Dendrochilum, the first are pendent and creeping plants that grow along an elongated and sometimes branching rhizome. The pseudobulbs are often spaced widely apart. The second growth habit is tufted plants where the pseudobulbs cluster together on short rhizomes.

The pendent and creeping plants are found in all species of the subgenus Dendrochilum and in many Sumatran species within subgenus Platyclinis section Eurybrachium. There are scattered species within subgenus Platyclinis section Platyclinis. Jeffrey Wood wrote that species with the first type of growth habit are generally found in sheltered habitat and hang from trees, scramble over rocks or the forest floor as a terrestrial (Wood 2001).

Cataphylls

New growths are covered by cataphylls while they are growing. The cataphylls disintegrate into persistent or non persistent fibres as the pseudobulbs mature. The presence of cataphylls at the time of flowering is of limited diagnostic or taxonomic value on a couple of species, for example Dendrochilum latifolium var latifolium and Dendrochilum latifolium var macranthum.

Pseudobulbs

Pseudobulb shape and size varies greatly between species. Some Borneo species of subgenus Platyclinis section Eurybrachium have orange, yellow, red and even red suffused with green coloured pseudobulbs.

Leaves

There are two types of ptyxis within Dendrochilum leaves; the leaves are either conduplicate or convolute. All Dendrochilum leaves are petiolate or nearly sessile. The subgenus Dendrochilum have the shortest petioles, some of the species are nearly sessile. The width of leaves can be of diagnostic importance within some species groups. Jeffrey Wood wrote that leaf width is of limited diagnostic value in Borneo taxa (Wood 2001). There are always distinct nerves any many indistinct nerves that run the length of the leaf, measuring the distance of the lateral nerves from the leaf margin can be of diagnostic value. The leaves generally have entire margins but minutely erose to undulate margins exist.

Some Borneo species within subgenus Platyclinis section Cruciformia have crystalline calcium oxalate bodies on the leaf blades.

Abnormalities of bifoliate leaves have been recorded on Dendrochilumpallidiflavens (Pederson pers com) and on one of my own plants (Dendrochilum undescribed species).

Inflorescence

There are three types of inflorescence found on Dendrochilum (Pedersen 1997).

Synanthous - the inflorescence grows from developing pseudobulbs and grows at the same time as the subtending leaf

Heteranthous - the inflorescence grows from the rhizome and does not go on to develop a new growth

Hysteranthous - the inflorescence develops after the leaf is fully developed.

Dendrochilum that have synanthous inflorescences and convolute leaves generally have the subtending leaf envelop the inflorescence to form a loose funnel. Dendrochilum that have synanthous inflorescences and conduplicate leaves have the peduncle free from the subtending leaf at the time of flowering. There are 10, probably 11 species from subgenus Acoridium section Acoridium where at least for a part the peduncle is enclosed by the subtending leaf, these species are; Dendrochilum graminifolium, Dendrochilum wenzelii, Dendrochilum javierii, Dendrochilum saccolabium, Dendrochilum perplexum, Dendrochilum tenellum, Dendrochilum stenophyllum, Dendrochilum williamsii, Dendrochilum luzonense, Dendrochilum louisianum (Pedersen 1997). The 11th species is probably the recently described Dendrochilum banksii.

The inflorescence is separated into a peduncle and a rachis. There are none or many non floriferous bracts at the proximal end of the rachis, these bracts separate the peduncle from the rachis. The inflorescence is either flexuose or has distichously alternating flowers. On some species such as Dendrochilum convallariaeforme and Dendrochilum propinquum the rachis twists to form a cylindrical spiral. The flowers open from either the proximal, central or distal part of the rachis, although most commonly from the proximal section. Species from the subgenus Acoridium section Convoluta often have distal opening flowers. The point from where the flowers open can be of diagnostic value.

Floral bracts

Henrik Pedersen wrote that floral bracts rarely contribute as factors of taxonomic diagnostic value (Pedersen 1997) and for this reason I have chosen not to include them in the descriptions on this website.

Flowers

Most Dendrochilum have resupinate flowers (labellum facing downwards) but a couple of described species have non-resupinate flowers, Dendrochilum scriptum, Dendrochilum propinquum, Dendrochilum cupulatum and Dendrochilum muluense.

Flower colour is of little diagnostic value and even though the flower colour is given within this website it should not be the basis of identification.

There are always three petals on a Dendrochilum flower, the lateral petals and a ventral petal, for the purposes of this website I have called the ventral petal the labellum. The petals are generally shorter and narrower than the sepals and are much more inclined to have erose, irregular or fimbriate margins.

There are always three sepals on a Dendrochilum flower, two lateral sepals and a dorsal sepal.

The sepals and petals are widely spreading, incurved or recurved. The sepals and petals are never bent at a right angle as they are in Pholidota. A couple of Borneo species within subgenus Platyclinis section Eurybrachium have petals that are twisted at 90 degrees from the vertical.

The labellum is always firmly attached to the column except in the subgenus Dendrochilum and subgenus Platyclinis sections Replicata and Platyclinis. In those sections the labellum is elastically attached to the column (Pedersen 1997). The way a labellum is attached to the column is of great diagnostic value at subgeneric and sectional level. The labellum can be 3-lobed, entire, obscurely 3-lobed, pandurate, bilobed, hastate and cruciform. There are two species with a cymbiform labellum, Dendrochilum cymbiforme and Dendrochilum magnum, to a lesser extent. A couple of Philippine species have a saccate labellum. The labellum is usually porrect or pendent, can recurve, decurve or even coil as can be seen in the pictures of Dendrochilum simile. Many Dendrochilum have a concave labellum, one species, Dendrochilumzollingeri is of particular interest because the labellum is concave at its apex.

Most Dendrochilum have ornaments on the labellum in the forms of calli or keels. Within the subgenera Pseudacoridium and Acoridium there are usually two lateral calli and one median callus, although this is not a general rule. There are usually two keels found on the labellum within subgenus Dendrochilum (Pedersen 1997).

The labellum is one of the most important taxonomic diagnostic features within the genus.

Column

The column is the most important taxonomic diagnostic feature within Dendrochilum at subgeneric, section, species and variety level. When trying to identify a species try to get a close up image of the column.

There is always a column in every Dendrochilum flower. There is either no column foot, a short column foot, or a prominent column foot. A column foot is of important diagnostic value at subgeneric and sectional level.

Within the subgenera Dendrochilum and Platyclinis section Platyclinis the apical hood is elongated. Other sections with Platyclinis have an apical hood that exceeds the anther cap. Within subgenera Pseudacoridium and Acoridium some species have an apical hood but it is small and covers the anther cap (Pedersen 1997). Jeffrey Wood wrote that the presence or absence of the apical hood indicates two streams of evolution within Dendrochilum subgenera, Pseudacoridium and Acoridium and the other stream Platyclinis and Dendrochilum (Wood 2001).

There are no stelidia in the subgenera Pseudacoridium and Acoridium. There are stelidia in the subgenera Dendrochilum and Platyclinis. The length, shape and position of the stelidia are of important diagnostic taxonomic importance.

Jeffrey Wood wrote a fascinating paragraph on the stelidia "Anatomical examination by Pederson (1997) failed to find any vascular traces of staminoda in the stelidia of the Philippine D. cobbianum and D. filiforme. The functional and, admittedly limited, anatomical evidence points to the stelidia being derived organs. Stelidia probably evolved only once in a common ancestor of subgenera Dendrochilum and Platyclinis, although reversals have probably taken place several times within subgenus Platyclinis"

Within this website I do not describe the rostellum, stigmatic cavity, anther cap or pollina.

Dendrochilum in Cultivation

There are only a fraction of Dendrochilum species found in cultivation and information about the specific habitat of many of them is hard to find or not known. For this reason I haven't been able to provide cultivation advice of many species on this website. Where culture advice has been given it is not always based on my own growing culture but is a combination of what I have read, experienced and talked to other people about. Remember what works for me might may not for you. A great article for general Dendrochilum culture was written by Jim Cootes and David Banks in Orchids Australia, 1995.

What most growers of Dendrochilum agree is that:

There should be plenty of air movement

The plants should be kept moist and never be allowed to dry out

Watering should be from the bottom and not from above the plant

Humidity must be high

There needs to be a difference between day and night temperature

Water should have low salinity

Growers vary with their preferred growing media but usually agree that the media should be moisture retentive. I prefer to use a mixture of lava pebble with sphagnum moss and fine grade bark. Species from subgenus Dendrochilum and some Sumatran species of subgenus Platyclinis section Eurybrachium should be mounted but watered and sprayed frequently. Growing Dendrochilum on mossy poles and moss covered branches is ideal and look more natural. I have experimented myself with this method and have had excellent results. I know some countries such as the USA are keen on semi hydroponics (S/H) but I have no experience or knowledge of growing Dendrochilum this way.

In the wild many Dendrochilum species are found in exposed conditions including ridge tops, cliff tops, outer tree branches, rock faces and the tree canopy. This indicates that plenty of air movement is essential for cultivating these species, a summary that my experiences confirm.

I have found that Dendrochilum species differ greatly from each other with their cultural requirements and I have found researching their habitat helps. For example, if a species is found on Mount Pulog, looking the mountain up on a search engine will give valuable information. I even search on You Tube to see if there are any amateur movies made of treks up the mountain in question. From researching you will see how light intensity, temperature and habitat varies and changes rapidly at different elevations. Getting to know what mossy forest looks like will help with the culture of many species. There are many cool to cold growing species of Dendrochilum as well as a few that grow in warmer climate. One Dendrochilum species can be found growing as high as 3,800 metres elevation, just 400 metres below the summit of Mount Kinabalu.

Identifying Dendrochilum

One thing I have found with this genus is that you should never assume identification unless you are absolutely sure and have ruled out all other possibilities by using recent published keys to the genus. I usually ask a Dendrochilum expert for their opinion even after establishing what I think the species could be. As I mentioned above, care needs to be applied if you are comparing your plant to a photo on the internet. Be careful of the accuracy of all photos found on forums, on line orchid encyclopaedias, photography sites, books, orchid society show tables, nursery catalogues and in particular plant lists from the Philippines. There are even awarded plants around the world that have been mis-labelled. Some Dendrochilum have a similar appearance and can only be easily identified from one another by minute features such as how far the lateral nerves are from the leaf margin, the position/shape of their calli, the keels, shape and margin type of the apical hood and the position of the stelidia. Some of these features can only be seen under a microscope or very powerful lens.

To help with any potential confusion each species page on this website comes with a similar species heading where you might want to check another similar looking species photo or plant description just to be sure.

Some species vary greatly, sometimes based on their natural demographics but sometimes this is just how they are. Species such as Dendrochilum wenzelii or Dendrochilum kingii have a variety of colour forms. Other species such as Dendrochilum glumaceum or Dendrochilum simplex can vary greatly in flower and plant size.

Some commonly mixed up species include Dendrochilum magnum with Dendrochilum latifolium var macranthum and Dendrochilum latifolium var latifolium. I have noticed on some USA forums that users have been incorrectly saying they are all the same species. Dendrochilum wenzelii and Dendrochilum javierii have been referred to Dendrochilum arachnites 'red' or 'yellow' a mistake perpetrated by Philippine orchid nurseries who import them to Australia, the USA and Europe. Even the odd herbaria have fallen for this particular mix-up. Dendrochilum cootesii is often mislabelled as Dendrochilum anfractum, a puzzle because Dendrochilum anfractum is not known in cultivation. Many other species are incorrectly identified on orchid encyclopaedias, Flickr and other sites because they are not validated by the site owners and photographers against herbariums specimens and genera experts; this in turns leads to mis-labelled plants and photos in personal collections.

Acknowledgements

There are a few people who have been very helpful with their information and contribution to this website.

Firstly I would like to thank Malcolm Perry and Jim Cootes. Thank you for the personal correspondence, photos, encouragement and for the editing of text.

Thank you to Ed de Vogel and the team at the National Herbarium in the Netherlands for supplying me with manuscripts from the archives of the National Herbarium in the Netherlands.

Thank you to Henrik Pedersen for all of the personal correspondence, information, manuscripts and photos.

Thank you to Jeffrey Wood and the Royal Botanic Gardens, Kew for the personal correspondence and for allowing me to use the bequeathed photos of the late Jim Comber, the photos from the Dendrochilum of Borneo and the Orchids of Borneo series.